The invention also includes a process of solubilizing a fat-soluble substance, especially a perfume oil, in a clear, stable, aqueous or aqueous-alcoholic solution by means of a hydroxyalkyl ether-ethoxylate of the formula ##STR6## wherein R1 and R2 independently of each other are a member selected from the group consisting of alkyl having 1 to 24 carbon atoms, preferably 12 to 18 carbon atoms, and